Resource availability and roosting ecology shape reproductive phenology of rain forest insectivorous bats

Bats in temperate and subtropical regions typically synchronize birth of a single young with peaks in resource availability driven by local climate patterns. In tropical rain forest, insects are available throughout the year, potentially allowing departures from seasonal monoestry. However, reproductive energy budgets may be constrained by the cost of commuting to foraging grounds from distant roosts. To test these hypotheses, we simultaneously tracked female reproductive activity of 11 insectivorous bat species, insect biomass, and local weather variables for 20 months in a Malaysian rain forest. Five species roost in forest structures and hence have low commuting costs, whereas six species depend on caves, which are limited in the landscape, and are presumed to incur higher commuting costs to foraging sites. Monthly insect biomass was positively correlated with monthly rainfall, and there was a significant relationship between insect biomass and lactation in cave‐roosting but not forest‐roosting species. Cave‐roosting species were seasonally monoestrus, with parturition confined to a two‐month period, whereas in forest‐roosting species, pregnancy and lactation were recorded throughout the year. Our results suggest that the energetic costs of commuting from roosts to foraging grounds shape annual reproductive patterns in tropical rain forest insectivorous bats. Ongoing changes in forest landscapes are likely to increase these costs for cave‐roosting bats, further restricting reproductive opportunities. Climate change is projected to influence the timing of rainfall events in many tropical habitats, which may disrupt relationships between rainfall, insect biomass, and bat reproductive timing, further compromising reproductive success.     

Climate and weather impact timing of emergence of bats

Interest in forecasting impacts of climate change have heightened attention in recent decades to how animals respond to variation in climate and weather patterns. One difficulty in determining animal response to climate variation is lack of long-term datasets that record animal behaviors over decadal scales. We used radar observations from the national NEXRAD network of Doppler weather radars to measure how group behavior in a colonially-roosting bat species responded to annual variation in climate and daily variation in weather over the past 11 years. Brazilian free-tailed bats (Tadarida brasiliensis) form dense aggregations in cave roosts in Texas. These bats emerge from caves daily to forage at high altitudes, which makes them detectable with Doppler weather radars. Timing of emergence in bats is often viewed as an adaptive trade-off between emerging early and risking predation or increased competition and emerging late which restricts foraging opportunities. We used timing of emergence from five maternity colonies of Brazilian free-tailed bats in south-central Texas during the peak lactation period (15 June-15 July) to determine whether emergence behavior was associated with summer drought conditions and daily temperatures. Bats emerged significantly earlier during years with extreme drought conditions than during moist years. Bats emerged later on days with high surface temperatures in both dry and moist years, but there was no relationship between surface temperatures and timing of emergence in summers with normal moisture levels. We conclude that emergence behavior is a flexible animal response to climate and weather conditions and may be a useful indicator for monitoring animal response to long-term shifts in climate.     

Functional significance of emergence timing in bats

We investigated intraspecific differences in evening emergence time of northern bats Eptesicus nilssonii , greater horseshoe bats Rhinolophus ferrumequinum and lesser horseshoe bats R. hipposideros. Significant differences in emergence time were associated with presumed variation in predation risk, related to light intensity, and energetic benefits of early emergence, caused by differences in age, reproductive state (energetic demands), and body condition. Females of both species emerged progressively later as pregnancy advanced, perhaps because of decreased flight performance, and earlier as lactation proceeded, probably because of increased energy demands and low reserves. Bats under energetic stress, due to persistent low ambient temperatures during pregnancy, or when body reserves were low, emerged relatively early, and hence appeared to take higher risks, than other bats. Young bats emerged much later than the adults at first, but progressively earlier as their flight skills improved. Lesser horseshoe bats emerged later at exposed roost exits than in more protected situations. The results largely corroborate the hypothesis that emergence time, and therefore feeding performance, of insectivorous bats is constrained at bright light conditions, possibly by predation risk (from birds), and modified by energetic considerations.     

Spatial and temporal patterns of roost use by tree-dwelling barbastelle bats Barbastella barbastellus

We evaluated the spatial and temporal patterns of roost switching behaviour by a tree-dwelling population of barbastelle bats Barbastella barbastellus in a beech forest of central Italy. Switching behaviour was common to both sexes and did not depend on group size. We observed both individual and group switching, the latter often involving the abandonment of a roost tree on a single night. We suggest that behaviours such as flight activity around roosts or cavity inspection by bats play a role in recruiting group mates and coordinating their occupation of another site. Bats almost never crossed mountain ridges to use roosts located beyond them, possibly because ridges are regarded as boundaries delimiting main roosting areas. The rate of switching was lowest during the middle of the lactation period, probably to minimise problems related to the transportation of non-volant young by their mothers. Although the maintenance of social relationship among bats spread over large forest areas may partly explain the occurrence of roost switching, the persistence of this behaviour in solitary bats and the movement of entire groups best fit the hypothesis that roost switching represents a way to maintain or increase knowledge of alternative roosts.     

Roost use by long-tailed bats in South Canterbury: examining predictions of roost-site selection in a highly fragmented landscape

We studied the roosting ecology of the long-tailed bat (Chalinolobus tuberculatus) during the springautumn months from 1998–2002 at Hanging Rock in the highly fragmented landscape of South Canterbury, South Island, New Zealand. We compared the structural characteristics and microclimates of roost sites used by communally and solitary roosting bats with those of randomly available sites, and roosts of C. tuberculatus occupying unmodified Nothofagus forest in the Eglinton Valley, Fiordland. Roosting group sizes and roost residency times were also compared. We followed forty radio-tagged bats to 94 roosts (20% in limestone crevices, 80% in trees) at Hanging Rock. Roosts were occupied for an average of 1 day and 86% were only used once during the study period. Colony size averaged 9.8 ± 1.1 bats (range 2–38) and colonies were dominated by breeding females and young. Indigenous forest, shrubland remnants and riparian zones were preferred roosting habitats. Communally roosting bats selected roosts in split trunks of some of the largest trees available. Selection of the largest available trees as roost sites is similar to behaviour of bat species occupying unmodified forested habitats. Temperatures inside 12 maternity roosts measured during the lactation period were variable. Five roosts were well insulated from ambient conditions and internal temperatures were stable, whereas the temperatures inside seven roosts fluctuated in parallel with ambient temperature. Tree cavities used by bats at Hanging Rock were significantly nearer ground level, had larger entrance dimensions, were less well insulated, and were occupied by fewer bats than roosts in the Eglinton Valley. These characteristics appear to expose their occupants to unstable microclimates and to a higher risk of threats such as predation. We suggest that roosts at Hanging Rock are of a lower quality than those in the Eglinton Valley, and that roost quality may be one of the contributory factors in the differential reproductive fitness observed in the two bat populations. The value of introduced willows (especially Salix fragilis) as bat roosts should be acknowledged. We recommend six conservation measures to mitigate negative effects of deterioration of roosting habitat: protection and enhancement of the quality of existing roosts, replanting within roosting habitat, provision of high quality artificial roosts, predator control, and education of landowners and statutory bodies.     

Sociality influences thermoregulation and roost switching in a forest bat using ephemeral roosts

In summer, many temperate bat species use daytime torpor, but breeding females do so less to avoid interferences with reproduction. In forest‐roosting bats, deep tree cavities buffer roost microclimate from abrupt temperature oscillations and facilitate thermoregulation. Forest bats also switch roosts frequently, so thermally suitable cavities may be limiting. We tested how barbastelle bats (Barbastella barbastellus), often roosting beneath flaking bark in snags, may thermoregulate successfully despite the unstable microclimate of their preferred cavities. We assessed thermoregulation patterns of bats roosting in trees in a beech forest of central Italy. Although all bats used torpor, females were more often normothermic. Cavities were poorly insulated, but social thermoregulation probably overcomes this problem. A model incorporating the presence of roost mates and group size explained thermoregulation patterns better than others based, respectively, on the location and structural characteristics of tree roosts and cavities, weather, or sex, reproductive or body condition. Homeothermy was recorded for all subjects, including nonreproductive females: This probably ensures availability of a warm roosting environment for nonvolant juveniles. Homeothermy may also represent a lifesaver for bats roosting beneath loose bark, very exposed to predators, because homeothermic bats may react quickly in case of emergency. We also found that barbastelle bats maintain group cohesion when switching roosts: This may accelerate roost occupation at the end of a night, quickly securing a stable microclimate in the newly occupied cavity. Overall, both thermoregulation and roost‐switching patterns were satisfactorily explained as adaptations to a structurally and thermally labile roosting environment.     

Roost preferences and foraging ranges of the eastern forest bat Vespadelus pumilus under two disturbance histories in northern New South Wales,Australia

Little is known about the habitat requirements of Australian bats; however, this information is needed to make better‐informed decisions when systems are disturbed. This study contrasts the roosting and foraging ecology of the eastern forest bat Vespadelus pumilus (Vespertilionidae), one of Australia’s smallest bats, between two sites of differing disturbance history on the mid‐north coast of New South Wales. Lorne Flora Reserve (182 ha) is primarily old‐growth forest surrounded by regrowth forest and eucalypt plantations, while Swans Crossing is dominated by regrowth and eucalypt plantations established on part of an old dairy farm. A total of 38 bats were tracked during the maternity and mating seasons at the two sites. Roost preferences were determined by comparing trees used as roosts with those randomly available, while foraging bats were triangulated from fixed stations at night. Bats tracked at Lorne Flora Reserve typically roosted in hollows within large, mature trees and showed a strong preference for roosting and foraging (females only) within the Reserve. Lactating females at Swans Crossing roosted in hollows of remnant rainforest trees within a gully and dead eucalypts, while males often roosted in understorey trees (such as Acacia). Dead trees were frequently used as roosts at both sites. Under both disturbance histories, the mean distance of female maternity roosts from creeks was 20 m, indicating that riparian zones provide important roosting habitat for V. pumilus. However, roosts shifted to the mid‐slope prior to winter when bats mate. Retention of mature trees in a variety of topographic locations may allow behavioural adjustments with the seasons. Bats caught in the regrowth forest also foraged there, with foraging ranges averaging just 5.3 ha (n = 10), indicating that regrowth is used by this bat for both foraging and roosting.     

Roost switching, roost sharing and social cohesion: forest-dwelling big brown bats, Eptesicus fuscus, conform to the fission-fusion model

We used radiotelemetry to quantify roost switching and assess associations between members of maternity colonies of forest-dwelling big brown bats. Bats remained loyal to small roosting areas of forest within and between years and switched trees often (). For radiotagged bats from the colony in one of these areas, roost-switching frequency was positively correlated with the number of different individuals with which tagged bats shared roosts. We quantified associations between pairs of bats using a pairwise sharing index and found that bats associated more often than predicted when roost and roostmate selection were random but that all tagged bats spent at least some days roosting in different trees, apart from preferred roostmates. Our results suggest that forest-dwelling big brown bats conform to a fission-fusion roosting pattern. Roost switching in forests may reflect the maintenance of long-term social relationships between individuals from a colony that is spread among a number of different trees on a given night. In this fission-fusion scenario, switching between trees, within a local area, could serve to increase the numbers of individuals with which bats maintain associations. We contend that roosting areas in forests are analogous to spatially large roosts in caves, mines and buildings.     

Male Seminole Bat Winter Roost-Site Selection in a Managed Forest

Abstract: Understanding year-round roost-site selection is essential for managing forest bat populations. From January to March, 2004 to 2006, we used radiotelemetry to investigate winter roost-site selection by Seminole bats (Lasiurus seminolus) on an intensively managed landscape with forested corridors in southeastern South Carolina, USA. We modeled roost-site selection with logistic regression and used Akaike's Information Criterion for small samples (AIC_c) and Akaike weights to select models relating roost-site selection to plot- and landscape-level variables. We tracked 20 adult male bats to 71 individual roosts. Bats used a variety of roosting structures, including the canopy of overstory trees, understory vegetation, pine (Pinus spp.) needle clusters, and leaf litter. Roost height, structure type, and habitat type were influenced by changes in minimum nightly temperature. On warmer nights, bats selected taller trees in mature forest stands, but when minimum nightly temperatures were <4° C, bats typically were found roosting on or near the forest floor in mid-rotation stands. We recommend avoiding prescribed burning in mid-rotation stands on days when the previous night's temperature is <4 °C to minimize potential disturbance and direct mortality of bats roosting on or near the forest floor. We encourage forest managers to incorporate seasonal changes in roost-site selection to create year-round management strategies for forest bats in managed landscapes.     

Night roosting and the nocturnal time budget of the little brown bat,Myotis lucifugus: Effects of reproductive status,prey density,and environmental conditions

Summary The insectivorous bat Myotis lucifugus typically apportions the night into two foraging periods separated by an interval of night roosting. During this interval, many bats occupy roosts that are used exclusively at night and are spatially separate from maternity roosts. The proportion of the night which bats spend roosting, and thus the proportion spent foraging, vary both daily and seasonally in relation to the reproductive condition of the bats, prey density, and ambient temperature. A single, continuous night roosting period is observed during pregnancy. During lactation, females return to maternity roosts between foraging bouts, and night roosts are used only briefly and sporadically. Maximum use of night roosts occurs in late summer after young become volant. Superimposed upon these seasonal trends is day-to-day variation in the bats' nightly time budget. Long night roosting periods and short foraging periods are associated with cool nights and low prey density. This behavioral response may minimize energetic losses during periods of food scarcity.     

Evening Bat Summer Roost-Site Selection on a Managed Pine Landscape

ABSTRACT Creation and maintenance of forested corridors to increase landscape heterogeneity has been practiced for decades but is a new concept in intensively managed southern pine (Pinus spp.) forests. Additionally, more information is needed on bat ecology within such forest systems. Therefore, we examined summer roost-site selection by evening bats (Nycticeius humeralis) in an intensively managed landscape with forested corridors in southeastern South Carolina, USA, 2003–2006. We radiotracked 53 (26 M, 27 F) adult evening bats to 75 (31 M, 44 F) diurnal roosts. We modeled landscape-level roost-site selection with logistic regression and evaluated models using Akaike's Information Criterion for small samples. Model selection results indicated that mature (≥40 yr) mixed pine-hardwood stands were important roost sites for male and lactating female evening bats. Upland forested corridors, comprised of mature pine or mixed pine-hardwoods, were important roosting habitats for males and, to a lesser extent, lactating females. Male roosts were farther from open stands and lactating female roosts were farther from mid-rotation stands than randomly selected structures. Our results suggest roost structures (i.e., large trees and snags) in mature forests are important habitat components for evening bats. We recommend maintaining older (>40 yr old) stand conditions in the form of forest stands or corridors across managed landscapes to provide roosting habitat. Furthermore, our results suggest that an understanding of sex-specific roost-site selection is critical for developing comprehensive guidelines for creating and maintaining habitat features beneficial to forest bats.     

The effect of logging on fission-fusion behaviour of tree-dwelling bats explored by an agent-based model

Logging is one of the greatest threats to global biodiversity, while forests are one of the most important habitats for bats. Bats that roost in tree cavities require a large number of potential roosts due to their frequent roost switching. However, the density of tree cavities and hollows sufficient to sustain large populations of bat species in forests is unknown. The fission-fusion dynamics of bat groups in forest environment is associated with ritualised dawn swarming behaviour at potential tree cavities that serves to exchange information in a non-centralised decision-making process. We used a computer model based on the swarm algorithm, SkyBat, that resembles this complex process and aimed to determine how population size changes over time when cavity trees are removed from roosting territory of the local population of Leisler's bats (Nyctalus leisleri), which inhabit a forest habitat in Central Europe. Simulations revealed that social bonds between bats, maintained by frequent switching among groups, play an important role in this highly dynamic system. When strong social contact was not considered, reducing the original number of trees with cavities (20 cavities × ha⁻¹) to 50% was still acceptable to bats, but further interventions and/or increased demand for social contact would have led to local extinction of the species. Results suggest that potential bat roosts in mature forest stands should be preserved as much as possible and that non-intensive logging and management can be beneficial to tree-dwelling bats.     

Effects of Hierarchical Roost Removal on Northern Long-Eared Bat (Myotis septentrionalis) Maternity Colonies

Forest roosting bats use a variety of ephemeral roosts such as snags and declining live trees. Although conservation of summer maternity habitat is considered critical for forest-roosting bats, bat response to roost loss still is poorly understood. To address this, we monitored 3 northern long-eared bat (Myotis septentrionalis) maternity colonies on Fort Knox Military Reservation, Kentucky, USA, before and after targeted roost removal during the dormant season when bats were hibernating in caves. We used 2 treatments: removal of a single highly used (primary) roost and removal of 24% of less used (secondary) roosts, and an un-manipulated control. Neither treatment altered the number of roosts used by individual bats, but secondary roost removal doubled the distances moved between sequentially used roosts. However, overall space use by and location of colonies was similar pre- and post-treatment. Patterns of roost use before and after removal treatments also were similar but bats maintained closer social connections after our treatments. Roost height, diameter at breast height, percent canopy openness, and roost species composition were similar pre- and post-treatment. We detected differences in the distribution of roosts among decay stages and crown classes pre- and post-roost removal, but this may have been a result of temperature differences between treatment years. Our results suggest that loss of a primary roost or ≤ 20% of secondary roosts in the dormant season may not cause northern long-eared bats to abandon roosting areas or substantially alter some roosting behaviors in the following active season when tree-roosts are used. Critically, tolerance limits to roost loss may be dependent upon local forest conditions, and continued research on this topic will be necessary for conservation of the northern long-eared bat across its range.     

Bats relocate maternity colony after the natural loss of roost trees

Understanding the ephemerality of trees used as roosts by wildlife, and the number of roost trees needed to sustain their populations, is important for forest management and wildlife conservation. Several studies indicate that roosts are limiting to bats, but few studies have monitored longevity of roost trees used by bats over several years. From 2004–2007 in Cypress Hills Interprovincial Park, Saskatchewan, Canada, several big brown bats (Eptesicus fuscus) from a maternity group roosted in cavities in trembling aspen (Populus tremuloides) trees approximately 7 km southeast away from their original known roosting area (RA1). Using a long-term data set of the roost trees used by bats in this area from 2000–2007, we evaluated whether the movement of bats to the new roosting area (RA4) corresponded with annual and cumulative losses of roost trees. We also determined whether longevity of the roosts from the time we discovered bats first using them differed between the 2 roosting areas based on Kaplan-Meier estimates. Bats began using RA4 in addition to RA1 in 2004, when the cumulative loss of roost trees in RA1 over 3 consecutive years reached 18%. Most bats exclusively roosted in RA4 in 2007, when the cumulative loss of roost trees over 6 consecutive years had reached 46% in RA1. Annual survival for roost trees, from when we first discovered bats using them, was generally lower in RA1 than in RA4. Our results suggest that the movement of bats to the new roosting area corresponded with high losses of roost trees in RA1. This provides additional evidence that to maintain high densities of suitable roost trees for bats in northern temperature forests over several decades, management plans need to recruit live and dead trees in multiple age classes and stages of decay that will be suitable for the formation of new cavities. © 2019 The Wildlife Society.     

Roosting and Foraging Behavior of Two Neotropical Gleaning Bats,Tonatia silvicola and Trachops cirrhosus (Phyllostomidae)1

We studied roosting and foraging behavior of two Neotropical gleaning bats, ?Orbigny's round-eared bat, Tonatia silvicola, and the fringe-lipped bat, Trachops cirrhosus (Phyllostomidae). Techniques included radio-tracking in a tropical lowland forest in Panama and analysis of data from long-term studies in Panama and Venezuela. Day roosts of T. silvicola were in arboreal termite nests. T. cirrhosus roosted in a hollow tree. T. silvicola emerged late (ca 60 min after sunset), and foraged close to the roosts (maximum distance 200–500 m). T. cirrhosus emerged early (ca 30 min after local sunset), and foraged farther from its roost (>1.5 km). Both bats used small foraging areas (3–12 ha) in tall, open forest. They foraged in continuous flight (maximum 27–36 min) or in short sally flights (<1 minute) from perches (“hang-and-wait” strategy). The small foraging areas of these bats and their sedentary foraging mode most likely make them vulnerable to habitat fragmentation.     

Winter Roosting Ecology of Eastern Red Bats in Southwest Missouri

Abstract: Eastern red bats (Lasiurus borealis) have been found to overwinter in areas that can experience severe fluctuations in temperature. We examined the red bat's use of winter roosts in southwest Missouri, USA, for 2 winters (2003–2005). We found tree roosts in eastern red cedars (Juniperus virginiana) and hardwoods. Tree roost sites were located on the south side of trees, and we found roost trees on south-facing slopes. Roost sites occurred more frequently in the location with least canopy cover. Bats switched from tree roosts to leaf litter roosts when ambient temperatures approached or fell below freezing. We found habitat characteristics and aspect to be determining factors in the selection of leaflitter roosts. Management of overwintering red bats requires a diverse forest structure, including canopy gaps, stand-density variation, and leaf-bearing trees, including oaks (Quercus spp.).     

Within‐season changes in habitat use of forest‐dwelling boreal bats

Bats utilize forests as roosting sites and feeding areas. However, it has not been documented how bats utilize these habitats in the boreal zone with methods afforded by recent technological advances. Forest structure and management practices can create a variety of three‐dimensional habitats for organisms capable of flight, such as bats. Here, we study the presence of boreal bats in a forest forming a mosaic of different age classes, dominant tree species, canopy cover, soil fertility, and other environmental variables, throughout their active season in the summer using passive ultrasound detectors. Our results indicate a preference for mature forest by Eptesicus nilssonii and a pooled set of Myotis bats. Both groups of bats also showed temporal changes in their habitat use regarding forest age. In June and July, both groups occurred more often in mature than young forests, but from August onwards, the difference in occurrence became less evident in Myotis and disappeared completely in E. nilssonii. In addition, E. nilssonii was more often present in forests with low canopy cover, and its occurrence shifted from coniferous forests to deciduous forests during the season. The results reflect the within‐season dynamics of bat communities and their ability to utilize different types of forest as environmental conditions change. Yet, the results most importantly emphasize the importance of mature forests to bat diversity and the need to conserve such environments in the boreal zone.     

Reconsidering the importance of harvested forests for the conservation of tree-dwelling bats

Intensively managed forests are often seen as of low priority to preserve forest bats. The main conservation strategy recommended, i.e. saving unmanaged “habitat islands” from logging to preserve some suitable habitat, detracts conservationists’ attention from ameliorating conditions for bats in harvested sites. We studied the threatened bat Barbastella barbastellus, mostly roosting in snags, in two beech forests: an unmanaged forest—the main maternity site—and a nearby, periodically logged area. We compared roost availability, roost use, capture rates, food availability and movement between these areas. The managed forest had a greater canopy closure, fewer dead trees, a smaller tree diameter and trees bearing fewer cavities than the unmanaged one. These differences helped explain the larger number of bats recorded in the unmanaged forest, where the sex ratio was skewed towards females. Prey availability was similar in both areas. We radiotracked bats to 49 day roosts. Five individuals caught in the managed area roosted in the unmanaged one at 6.7–8.2 km from the capture site. Few bats roosted in the managed forest, but those doing so proved flexible, using live trees and even rock crevices. Therefore, bats utilise areas in the matrix surrounding optimal roosting sites and sometimes roost there, highlighting the conservation potential of harvested forests. Besides leaving unmanaged patches, at least small numbers of dead trees should be retained in logged areas to favour population expansion and landscape connectivity. Our findings also question the validity of adopting presence records as indicators of forest quality on a site scale.     

The effect of bark beetle infestation and salvage logging on bat activity in a national park

Salvage logging—the removal of dead trees in disturbed forest stands—has been controversially discussed. We investigated the impact of bark beetle attacks and subsequent salvage logging on insectivorous bats in a temperate mountain forest. We quantified bat activity (25,373?min counts; 32 plots) using batcorders during 221 all-night surveys in stands killed by bark beetles, with dead trees removed or not, and in vital, single- or multi-layered mature forest stands. We analysed the differences in activity of all bats in general and of bats of foraging guilds (open habitat, forest edge, closed habitat) in these habitats using a generalized linear Poisson mixed model, with plot and observation as random factors, and temperature and habitat as fixed factors. Only open-habitat foragers were slightly more active in salvage-logged stands than in bark-beetle-affected stands; they generally benefited from an open forest canopy, whereas closed-habitat foragers did not. Our results indicated that: (1) bats are less affected by salvage logging after a disturbance of a magnitude typical for European forests, probably because enough roosts are present in surrounding areas, (2) habitats for open foragers are improved by bark beetle infestation and (3) bats are poor bioindicators of negative impacts of salvage logging after natural disturbance in forests with a composition typical for Central Europe.     

Roosting Behavior of Colonial and Solitary Flying Foxes in American Samoa (Chiroptera: Pteropodidae)1

We examined characteristics of roosting sites utilized by two flying fox species (Pteropus tonganus and P. samoensis) in American Samoa. The colonial roosting sites of P. tonganus were observed over a ten‐year period, including two years when severe hurricanes devastated bat populations and destroyed roost trees. Prior to the hurricanes, roosts were located on cliff faces above the ocean or steep mountainsides, locations that were either inaccessible to people or in protected areas where hunting was not allowed. In the years immediately following the hurricanes, P. tonganus colonies split into smaller groups that moved frequently to different locations. Four years after the second hurricane, colonies had coalesced and returned to many of the traditional roosting sites used before the hurricanes. Common tree species in upland and coastal forest were selected as roosts. The isolated locations selected for P. tonganus roosts were apparently the result of hunting pressure on the colonies. The solitary roosts of P. samoensis were observed during 29 months. Roosting bats were well concealed and hard to detect within the forest; even bats on exposed branches were cryptic. Mature primary forest was favored as roosting habitat. Individual bats used specific branches or trees as roosts and returned to them for up to 29 months. Unlike P. tonganus, people did not alarm roosting P. samoensis easily and some roosts were located near houses and along roads.